Spin Biochemistry:  Magnetic Isotope Effect in the Reaction of Creatine Kinase with CH<sub>3</sub>HgCl

Бучаченко, А. Л.; Kouznetsov, Dmitrii; Shishkov, Alexandre V.

doi:10.1021/jp030450o

Cited by 61 publications

(50 citation statements)

References 12 publications

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“…We suggest this polymerization reaction of sulfur product is mediated by an ion-radical mechanism similar to that proposed by Buchachenko et al (26). Here RSH acts as an electron donor to RSSH, forming an ion-radical pair intermediate that is initially in a singlet state.…”

Section: Resultssupporting

confidence: 73%

“…In Carius tube experiments, 33 S enrichments in acid volatile sulfide (AVS) and CRS products were small to undetectable except when S 8 or Na 2 S 2 O 4 was added (see Table S2) to catalyze reduced sulfur production in the reaction products with no effect to the S-radical chemistry. We speculate that the observed isotope effect originates from ion-radical pair (RS • H þ ∕RS • SH) intermediates (24,26) through the following sequence of reactions:…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Evidence of magnetic isotope effects during thermochemical sulfate reduction

Oduro

Harms

Sintim

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Thermochemical sulfate reduction experiments with simple amino acid and dilute concentrations of sulfate reveal significant degrees of mass-independent sulfur isotope fractionation. Enrichments of up to 13‰ for 33 S are attributed to a magnetic isotope effect (MIE) associated with the formation of thiol-disulfide, ion-radical pairs. Observed 36 S depletions in products are explained here by classical (mass-dependent) isotope effects and mixing processes. The experimental data contrasts strongly with multiple sulfur isotope trends in Archean samples, which exhibit significant 36 S anomalies. These results support an origin other than thermochemical sulfate reduction for the mass-independent signals observed for early Earth samples.anomalous | sulfur radical | thermolysis | spin-selective | hyperfine coupling S ince the report by Farquhar et al., (1) that significant deviations from the terrestrial fractionation line are observed in samples older than approximately 2.32-2.45 Ga (2, 3), considerable effort has been dedicated to identifying the origin and significance of this signal (4-10). The mass-independent signal in these ancient samples is expressed as variations in both Δ 33 S and Δ 36 S (1).* Given the observations that gas-phase reactions can produce mass-independent signals for both Δ 33 S and Δ 36 S, the first studies on this subject attributed this ancient signal to photolytic reactions in the early atmosphere. Subsequent studies also pointed out that the mass-independent reactions may also be produced by variations in the spectrum of light that drives atmospheric photolytic reactions (10-12), and other studies speculated that liquid phase reactions involving weakly bound transition states may account for these variations (7,13).In a recent report, Watanabe et al. (7) demonstrated that high temperature reduction of sulfate using alanine and glycine as organic substrates caused moderate mass-independent sulfur isotope fractionations. These authors did not identify the origin of the effect, but suggested that it was either a magnetic isotope effect (MIE) (14) or another type of isotope effect accompanying heterogeneous reactions such as adsorption of S-bearing compounds on surfaces of solids (13). Magnetic isotope effects are expressed in rare cases for isotopes with nuclear magnetic moments, like 13 C, 17 O, 29 Si, 199 Hg, 201 Hg, 73 Ge, 235 U, and 33 S (14, 15, 16). The effect is expressed when the lifetime of a radical pair is sufficient for hyperfine coupling between magnetic nuclei and unpaired electrons to influence interconversions between singlet and triplet states. This coupling in turn changes the proportion of reactive intermediates that can participate in spin-selective reactions. The 33 S nucleus has a spin of 3∕2 and a magnetic moment of 0.643 nuclear magnetons and has been implicated in at least one well-characterized example of a 33 S MIE (14,(17)(18)(19). The alternative suggestion relates to a proposal that anomalous isotope effects may be associated with heterogeneous reactions as a resu...

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Section: Resultssupporting

confidence: 73%

Section: Resultsmentioning

confidence: 99%

Evidence of magnetic isotope effects during thermochemical sulfate reduction

Oduro

Harms

Sintim

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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“…In a series of papers by Buchachenko and Kuznetsov (BK) together with various co-workers (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22), a radical pair mechanism has been proposed for enzymatic phosphorylation of adenosine diphosphate (ADP) to adenosine triphosphate (ATP). This mechanism is influenced by the presence of a magnesium isotope with a nuclear spin.…”

mentioning

confidence: 99%

Reexamination of magnetic isotope and field effects on adenosine triphosphate production by creatine kinase

Crotty

Silkstone

Poddar

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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The influence of isotopically enriched magnesium on the creatine kinase catalyzed phosphorylation of adenosine diphosphate is examined in two independent series of experiments where adenosine triphosphate (ATP) concentrations were determined by a luciferase-linked luminescence end-point assay or a real-time spectrophotometric assay. No increase was observed between the rates of ATP production with natural Mg, 24 Mg, and 25 Mg, nor was any significant magnetic field effect observed in magnetic fields from 3 to 1,000 mT. Our results are in conflict with those reported by Buchachenko et al. [J Am Chem Soc 130:12868–12869 (2008)], and they challenge these authors’ general claims that a large (two- to threefold) magnetic isotope effect is “universally observable” for ATP-producing enzymes [Her Russ Acad Sci 80:22–28 (2010)] and that “enzymatic phosphorylation is an ion-radical, electron-spin-selective process” [Proc Natl Acad Sci USA 101:10793–10796 (2005)].

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“…The magnetic isotope effect for mercury has been investigated and claimed to be observed in the reaction of kreatine kinase and methylmercury by gas source mass spectrometry (Buchachenko et al, 2004) and in the photolysis of Bis(p-trifluoromethylbenzyl)mercury by nuclear magnetic resonance (Buchachenko et al, 2007). Hg isotope fractionation during photoreduction of Hg 2+ and MeHg in the presence of dissolved organic carbon (DOC) in aqueous solution was conducted by Bergquist and Blum (2007) using CV-MC-ICP-MS and showed 199 Hg and 201 Hg isotope enrichment for mercury remaining in solution relative to MDF.…”

Section: Isotope Fractionation Lawsmentioning

confidence: 99%

“…Recent works denoted significant non-mass-dependent fractionation (NMF) of the odd isotopes ( 199 Hg and 201 Hg) of mercury in biogeological samples (Jackson et al, 2006;Bergquist and Blum, 2007;Epov et al, 2008;Biswas et al, 2008;Ghosh et al 2008;Jackson et al, 2008). In contrast to MDF, which is governed by chemical energy of the starting and transition states of reactant molecules, NMF reported on Hg isotopes in experimental and natural processes have been suggested to result from either magnetic interactions (magnetic isotope effect) (Buchachenko et al, 2004;Bergquist and Blum, 2007;Buchachenko et al, 2007) or from nuclear volume effects (also known as nuclear field shift effect) (Schauble, 2007).…”

Section: Introductionmentioning

confidence: 99%